#include "sha256.h"

namespace TSBLib {

    // 初始化 SHA256 的常量表
    const SHA256::WORD SHA256::k[64] = {
       0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,
       0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
       0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,
       0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
       0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,
       0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
       0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,
       0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
       0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,
       0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
       0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,
       0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
       0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,
       0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
       0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,
       0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
    };

    // 构造函数：初始化 SHA256 上下文
    SHA256::SHA256() {
        sha256_init();
    }

    // 初始化 SHA256 上下文
    void SHA256::sha256_init() {  
        ctx.datalen = 0; 
        ctx.bitlen = 0; 
        ctx.state[0] = 0x6a09e667; 
        ctx.state[1] = 0xbb67ae85; 
        ctx.state[2] = 0x3c6ef372; 
        ctx.state[3] = 0xa54ff53a; 
        ctx.state[4] = 0x510e527f; 
        ctx.state[5] = 0x9b05688c; 
        ctx.state[6] = 0x1f83d9ab; 
        ctx.state[7] = 0x5be0cd19; 
    }  

    // 更新 SHA256 上下文
    void SHA256::update(const void* data, size_t len) {  
        const BYTE* d = static_cast<const BYTE*>(data);
        for (size_t i = 0; i < len; ++i) {
            ctx.data[ctx.datalen] = d[i]; 
            ctx.datalen++; 
            if (ctx.datalen == 64) { 
                sha256_transform(ctx.data); 
                ctx.bitlen += 512; 
                ctx.datalen = 0; 
            }  
        }  
    }  

    // 最终计算 SHA256 哈希
    void SHA256::sha256_final(BYTE hash[]) {  
        WORD i = ctx.datalen; 
    
        // 填充剩余数据
        if (ctx.datalen < 56) { 
            ctx.data[i++] = 0x80; 
            while (i < 56) 
                ctx.data[i++] = 0x00; 
        }  
        else { 
            ctx.data[i++] = 0x80; 
            while (i < 64) 
                ctx.data[i++] = 0x00; 
            sha256_transform(ctx.data); 
            memset(ctx.data, 0, 56); 
        } 
    
        // 添加消息长度（以比特为单位，64 位大端）
        ctx.bitlen += ctx.datalen * 8; 
        ctx.data[63] = ctx.bitlen;
        ctx.data[62] = ctx.bitlen >> 8;
        ctx.data[61] = ctx.bitlen >> 16;
        ctx.data[60] = ctx.bitlen >> 24;
        ctx.data[59] = ctx.bitlen >> 32;
        ctx.data[58] = ctx.bitlen >> 40;
        ctx.data[57] = ctx.bitlen >> 48;
        ctx.data[56] = ctx.bitlen >> 56;
        sha256_transform(ctx.data); 
    
        // 将结果转换为字节数组（大端）
        for (i = 0; i < 4; ++i) { 
            hash[i]      = (ctx.state[0] >> (24 - i * 8)) & 0x000000ff; 
            hash[i + 4]  = (ctx.state[1] >> (24 - i * 8)) & 0x000000ff; 
            hash[i + 8]  = (ctx.state[2] >> (24 - i * 8)) & 0x000000ff; 
            hash[i + 12] = (ctx.state[3] >> (24 - i * 8)) & 0x000000ff; 
            hash[i + 16] = (ctx.state[4] >> (24 - i * 8)) & 0x000000ff; 
            hash[i + 20] = (ctx.state[5] >> (24 - i * 8)) & 0x000000ff; 
            hash[i + 24] = (ctx.state[6] >> (24 - i * 8)) & 0x000000ff; 
            hash[i + 28] = (ctx.state[7] >> (24 - i * 8)) & 0x000000ff; 
        }  
    }

    // 返回最终的 SHA256 哈希值（十六进制字符串）
    std::string SHA256::final() {
        BYTE hash[SHA256_BLOCK_SIZE];
        sha256_final(hash);
    
        // 将哈希值转换为十六进制字符串
        std::stringstream ss;
        ss << std::hex << std::setfill('0');
        for(int i = 0; i < SHA256_BLOCK_SIZE; ++i) {
            ss << std::setw(2) << static_cast<int>(hash[i]);
        }
        return ss.str();
    }

    // SHA256 核心转换函数
    void SHA256::sha256_transform(const BYTE data[]) {  
        WORD a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
      
        // 复制数据到消息块 m[0..63]
        for (i = 0, j = 0; i < 16; ++i, j += 4)
            m[i] = (data[j] << 24) | (data[j+1] << 16) | (data[j+2] << 8) | (data[j+3]);
        for ( ; i < 64; ++i)
            m[i] = SIG1(m[i-2]) + m[i-7] + SIG0(m[i-15]) + m[i-16];
      
        // 初始化工作变量
        a = ctx.state[0];
        b = ctx.state[1];
        c = ctx.state[2];
        d = ctx.state[3];
        e = ctx.state[4];
        f = ctx.state[5];
        g = ctx.state[6];
        h = ctx.state[7];
      
        // 主循环
        for (i = 0; i < 64; ++i) {
            t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
            t2 = EP0(a) + MAJ(a,b,c);
            h = g;
            g = f;
            f = e;
            e = d + t1;
            d = c;
            c = b;
            b = a;
            a = t1 + t2;
        }
      
        // 更新哈希值
        ctx.state[0] += a;
        ctx.state[1] += b;
        ctx.state[2] += c;
        ctx.state[3] += d;
        ctx.state[4] += e;
        ctx.state[5] += f;
        ctx.state[6] += g;
        ctx.state[7] += h;
    }

}
